The calcitonin/calcitonin gene related peptide (CT/CGRP) gene is expressed in a highly cell-specific fashion in the neuroendocrine system (Rosenfeld, M. G., et al. (1983) Nature 304, 129-135; Rosenfeld, M. G., Amara, S. G., Evans, R. M. (1984) Science 225, 1315-1320). Alternative splicing leads to the selective expression of either calcitonin mRNA in thyroid C cells or the neuropeptide CGRP in central and peripheral neurons (Rosenfeld, M. G., et al. (1983).
Certain members of the superfamily of steroids and retinoids confer further transcriptional regulation of the CT/CGRP gene. For example, glucocorticoid treatment increases mRNA levels of the CT/CGRP gene in rat thyroid in vivo (Besnard, P., Jousset, V., and Garel, J. M. (1989) FEBS Lett. 258, 293-296) as well as in human TT and rat CA77 medullary thyroid carcinoma cell lines (Cote, G. J., and Gagel, R. G. (1986) J. Biol. Chem. 261, 15524-15528; Muszynski, M., Birnbaum, R. S., and Roos, B. A. (1983) J. Biol. Chem. 259, 11678-11683; Russo, A. R., et al, (1988) J. Biol. Chem. 263, 5-8). However, glucocorticoid treatment decreases expression in rat 44-2C medullary thyroid carcinoma cells (Zeytin, F. N., Rusk, S., and Leff, S. E. (1987) Endocrinology 121, 361-370). Vitamin D has also been shown to inhibit calcitonin/CGRP expression in vivo (Naveh-Many, T., and Silver, J. (1988) J. Clin. Invest. 81, 1-14).
Both Calcitonin and CGRP play important biological roles. Calcitonin acts in the regulation of bone and mineral metabolism. Therapeutic application of calcitonin prevents bone resorption and is useful in the treatment of Paget's disease, hypercalcemia and osteoporosis (Physicians Desk Reference (1987) Medical Economic Company, Inc., Oradell, N.J., 41.sup.st ed.). Furthermore, calcitonin has also been implicated in pain suppression and may have potential uses as an analgesic (Copp, D. H. (1992) Endocrinology 131, 1007-1008). The CGRP gene product is a neurotrophic factor, a potent vasodilator, and acts in cardiovascular and gastrointestinal homeostasis (Leff, S. E., Rosenfeld, M. G., and Evans, R. M. (1986) Annu. Rev. Biochem. 55, 1097-1117; Fontaine, B. et al. (1986) Neurosci. Lett. 7, 59-65; New, H. V. and Mudge, A. W. (1986) Nature 323, 809-811; Denis-Donini, S. (1989) Nature 339, 701-704).
Previous work had identified a 520 bp region of the CT/CGRP upstream regulatory region responsible for cell-specific enhancement of basal transcription (Stolarsky-Fredman, L., et al. (1990) Mol. Endo. 4, 497-504). However, the specific regulatory elements and transcription factors required for the highly restricted expression of the CT/CGRP gene had yet to be identified.